The Summarit-S 70 mm f/2.5 ASPH. plays the role of the standard lens in the Leica S-System lens-portfolio, and has a focal length corresponding to 56 mm in 35 mm format. In order to ensure its universal versatility, the Leica design engineers invested immense effort to guarantee superior image performance at maximum aperture and at all focusing distances.
One of the eight lenses arranged in six groups features an aspherical surface, to minimize aberration effects.The two cemented elements are manufactured from glass with high anomalous partial dispersion, minimizing the effect of chromatic aberrations. In addition, glasses with very high refractive indices work together with the aspherical element to almost completely eliminate monochromatic aberration effects. In order to achieve perfect image performance from infinity to its minimum focusing distance of just 50 cm (~1.6 ft), the last two lenses are constructed as a floating element that moves independently from the rest of the optical system when focusing. The Leica Summarit-S 70 mm f/2.5 ASPH. is ideally protected against water droplets and dust and features a protective neutral glass filter that is included as a parameter in its optical design.
The reward for the immense effort invested in its design and construction is a lens with extraordinarily good contrast performance wide open and at all other apertures that, even at its closest focusing distances, can be only marginally improved in the extreme corners of images by stopping down. With a value of only 1.2%, distortion remains imperceptible, and maximum vignetting of 1.4 stops at maximum aperture is so extremely low, ensuring that the Leica Summarit-S 70 mm f/2.5 ASPH. delivers consistently dependable and superior image performance at all apertures and distances.